Can You Use Lice Shampoo Two Days In A Row To Kill Lice Faster?

This post will show you how to use lice shampoo properly and help you answer the question “Can you use lice shampoo two days in a row?” If you are considering doing this, read on.

While it’s great to see your kids have fun with their friends, there’s always a chance they catch lice from other children. The worst thing is that it may take up to six weeks for you to find out, by which time your kids have already suffered from itchiness and other symptoms.

Fortunately, lice shampoo – an over-the-counter medication – can help you treat lice at home. That said, is it the same as medicine and must be used by prescriptions?

Or, can you use lice shampoo two days in a row as well as anytime you want to? 

Can you use lice shampoo two days in a row
Can you use lice shampoo two days in a row

How Does Lice Shampoo Work?

When it comes to lice treatment, there are over-the-counter antiparasitic shampoos, prescription pediculicide shampoos, and pediculicide prescription lotions, with an increasing level of defense against lice. 

Among these, lice shampoos are considered the first line of defense. Their active ingredient is Permethrin (1%), a drug that treats lice and multiple other parasites. Permethrin attacks the bugs’ nervous systems, obliterates them, and causes death. 

With this active ingredient, lice shampoos can kill lice, but not nits or their pre-hatched eggs. To eradicate nits, you need a lice shampoo containing ovicide, a substance that can kill egg cells. 

Rather than permethrin, some lice treatment medications rely on a combination of pyrethrins and piperonyl butoxide. Pyrethrins, whose role is to paralyze and kill lice, are naturally occurring insecticides extracted from chrysanthemums. 

As a result, those allergic to chrysanthemums cannot use this medication. Meanwhile, piperonyl butoxide is added to increase the effective duration of pyrethrins. 

It may take one use of this medication to eliminate lice infestation while lice may die after 24 hours at most. In case there are still living lice, users will need to use it again after seven to ten days after the first application. 

Can You Use Lice Shampoo Two Days In A Row?

Most lice shampoos with active ingredients must not be used multiple times in a row. Generally speaking, it may take lice shampoos a few days to take effect, so you need to wait until you can perform the next treatment. 

The break between lice shampoo uses usually lasts for 9 to 10 days. When nits hatch, you can use lice shampoos again.

That said, there are lice shampoos that allow for everyday use. Therefore, the most important thing to keep in mind is always following the product’s instructions. 

Lice shampoos need a few days to take effect
Lice shampoos need a few days to take effect

How To Use Lice Shampoo?

Follow this step-by-step guide to treat your condition with lice shampoo.

  1. Spread the product all over your dry hair and start massaging. Make sure the shampoo covers all your hair, including the hair close to the scalp, the area behind your ears, and the back of your neck. 
  2. Rub some water on your head and work up some foam. Rinse your hair off with warm water then towel dry it. 
  3. Part your damp hair into four sections, comb each of them at a time with a lice comb. Start from the top of your head and motion to the end of your hair. Clean the comb throughout the process with clean tissues.
  4. Once you’re done combing, check your head again for lice and nits. Seal the bag of discarded tissues and throw it away. 
  5. Check your head again after seven days and repeat the treatment if you still find lice or nits.
To make sure the lice are gone, you need to check your hair regularly after washing your hair with a lice shampoo
To make sure the lice are gone, you need to check your hair regularly after washing your hair with a lice shampoo

Side effects of lice shampoo

Even with normal doses, lice shampoos can still cause side effects, the unwanted responses you may experience when using any medication. 

The side effects of lice shampoos range from light to severe, temporary to permanent. It’s best to watch out for symptoms during the process, including pain, itchiness, skin redness, swelling, warmth, and discharge. 


Are lice shampoo safe for toddlers?

This depends on what ingredient your shampoo contains.

Some lice shampoos like permethrin lotion 1% are safe for children of 2 months and older.

Meanwhile, lice shampoos containing Pyrethrins can only be used for children of 2 years and older. 

Is it harmful to overuse lice shampoo?

Yes, it is. While there are lice shampoo that can be used every day, overuse of the product takes a toll. 

The FDA warns overusing lice shampoo can cause neurological damage. You should always read the instruction carefully before covering your child’s head with lice shampoo. 

What are the side effects of lice shampoos on my hair?

Those whose hair has been dyed recently will see its color fade when using lice shampoo. However, this can only happen if you have to use it more than once. 

There’s no concrete evidence linking lice shampoo and dandruff. Yet, the active ingredient in lice shampoo will likely cause scalp dryness or irritation that eventually results in dandruff. 

Can you leave lice shampoo on overnight?

Not really. You need to follow the instructions for the product. For example, with permethrin 1%, you can leave it for 10 minutes only.

How long do lice live on mattresses?

Lice can survive for only 24 hours on surfaces without food, which is human blood. So, without their food source, lice will die after 1 or 2 days on mattresses. 

How do I check myself for lice?

If you suspect yourself has lice, you can check by following these steps: 

  1. Wet your hair. 
  2. Part your hair using a fine-toothed comb and use a flashlight to shine the scalp. 
  3. Look for brown insects moving on the scalp or nits stuck to the hair.

Final thoughts

To sum up, in most case you cannot use lice shampoo two days in a row. You should wait for at least nine days for the medication to work then check for lice. 

Especially lice shampoo overuse can cause neurological damage, so be extra careful when applying the product to your child’s head.


I am Jessica Coles, a hairstyling and trends expert who also holds a master's degree in cosmetology. I am one of the leading hair care experts who has been offering support round the clock.

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